Recently, this question asked whether you could Counterspell a spell without a material component that completely eliminates component requirement via Subtle Spell. The answer was no, with a Crawford Tweet as evidence. The following was asked in response to the Tweet but never answered and is a situation likely to occur in a campaign I'm running:

A Sorcerer uses Subtle Spell on a no-cost material component spell like Sleep or Fireball which they cast with a small crystal Arcane Focus kept tightly gripped and hidden in their fist.

In previous editions, spell descriptions indicated how materials were to be used: sprinkling sand or rose petals for Sleep, or throwing a ball of bat guano for Fireball. 5e doesn't provide these, nor does it seem likely such usages are possible with a Spellcasting Focus.

So, in this situation, is there enough information for another spellcaster to realise a spell is being cast for them to Counterspell?

\$\begingroup\$@V2Blast This question was asked in response to Crawford's Tweet by Cleric-of-Zarconis. Unfortunately, there was no answer.\$\endgroup\$
– TenryuMay 17 '18 at 0:11

\$\begingroup\$His tweet does seem slightly different from (and more specific than) my question above: "What if I'm 1) Holding a small focus in your pocket to hide it 2) Always holding the focus so it doesn't look suspicious?" But you're right, it is attempting to ultimately ask for the same reason.\$\endgroup\$
– V2BlastMay 17 '18 at 0:23

\$\begingroup\$@V2Blast It just says you have to handle the spellcasting focus but doesn't provide any detail. As I mentioned in my question it isn't possible to handle a focus in the same manner as material components. It still doesn't tell me whether this would be noticeable to another caster or not.\$\endgroup\$
– TenryuMay 18 '18 at 8:25

2

\$\begingroup\$I've edited my answer with new sources for my claims, which I've only recently found. You may want to revise it.\$\endgroup\$
– BlueMoon93Mar 29 at 13:12

3 Answers
3

The Material Component of a spell only requires you to have a hand free and be able to access the arcane focus - it does not require any gestures (where the Somatic comes in) or articulations (Verbal).

Material (M)

A spellcaster must have a hand free to access these components, but it can be the same hand that he or she uses to perform somatic components. (PHB 203)

For Arcane Foci, you must only wield it to satisfy the Material component of the spell. Just as wielding a sword is not a perceptible attack, merely wielding an Arcane Focus and casting something with Subtle Spell will not make the spell perceptible.

\$\begingroup\$Also, it seems my question above (in the comments on the question itself) is addressed in the Sage Advice Compendium, in response to: "What’s the amount of interaction needed to use a spellcasting focus? Does it have to be included in the somatic component?"\$\endgroup\$
– V2BlastMay 18 '18 at 6:14

3

\$\begingroup\$-1: It requires you to draw your arcane focus if you aren't already wielding it. Additionally the arcane focus doesn't say it is subtle when wielded this way (it could glow, or require a particular level of concentration to utilise, resulting in perceptible effects on the caster's face)\$\endgroup\$
– illustroMar 28 at 11:19

\$\begingroup\$@illustro The SA that V2Blast links to uses the word "handle". There is no proscription on how subtle it is, and certainly nothing that says it glows or that there are any facial effects. You're stretching, trying to create another hidden rule or gatcha.\$\endgroup\$
– T.J.L.Mar 28 at 14:08

3

\$\begingroup\$@T.J.L.I'm not actually. I'm following the rules provided in XGtE (see BlueMoon's answer for the relevant quotes). The point I'm making is that this answer assumes "merely" wielding an Arcane Focus is not perceptible, which is not how the rules for this situation actually work.\$\endgroup\$
– illustroMar 28 at 14:10

RaW, yes, the spell could still be countered.

If the spell has a material component, you're not able to hide it. Nothing in the RaW claims that you can hide the casting of a spell by using a small arcane focus or something else. In fact, from XGtE, p. 85, "Perceiving a Caster at Work":

To be perceptible, the casting of a spell must involve a verbal, somatic, or material component. The form of a material component doesn’t matter for the purposes of perception, whether it’s an object specified in the spell’s description, a component pouch, or a spellcasting focus.

It's irrelevant whether the Arcane Focus is small or not, you cannot hide the casting of a spell with it. The only way to make casting imperceptible is to remove the Material, Somatic and Verbal components. From XGtE, same section:

If the need for a spell’s components has been removed by a special ability, such as the sorcerer’s Subtle Spell feature or the Innate Spellcasting trait possessed by many creatures, the casting of the spell is imperceptible.

\$\begingroup\$The passages you cite establish simply that a component is a necessary condition not a sufficient one. There is simply no basis for a blanket "you cannot hide a spell cast".\$\endgroup\$
– Benjamin OlsonApr 20 at 22:46

2

\$\begingroup\$@BenjaminOlson If nothing says you can, and there are no hidden rules, then my interpretation is that you cannot hide casting spells.\$\endgroup\$
– BlueMoon93Apr 21 at 0:06

\$\begingroup\$@BlueMoon93 In D&D, as in the Anglo-American legal tradition, "everything which is not forbidden is allowed". Nothing says you can not, merely that detection is possible, perhaps easy.\$\endgroup\$
– Benjamin OlsonApr 21 at 6:07

1

\$\begingroup\$@BenjaminOlson i'm not sure if I'm being trolled, but by that logic, my half-orc can shoot lasers from his eyes, since nowhere does it say he can't\$\endgroup\$
– BlueMoon93Apr 21 at 9:18

\$\begingroup\$You would have to ask the DM about that. Other than being called "lasers", comparable magical powers aren't exactly unheard of in the game. Would it really verisimilitude more than making all people instantly aware of any spellcaster's spellcasting regardless of circumstance?\$\endgroup\$
– Benjamin OlsonApr 21 at 18:02

It Could be Countered Sometimes, But it has to Actually be Detected

To be perceptible, the casting of a spell must involve a verbal, somatic, or material component.

Hence one or more of these components is a necessary precondition to perceiving the casting (to the extent we enforce materials in Xanathar's Guide to Everything). An arcane focus of any kind may make it possible to perceive. However it is not clear that all arcane foci under all circumstances would actually be perceived, simply that they are one of the things that make it possible to perceive.

For counterspell specifically, we see:

Casting Time: 1 reaction, which you take when you see a creature within 60 feet of you casting a spell.

It is not sufficient simply that the spell be perceptible in some way; it must actually be perceived and be perceived via the sense of sight specifically to be a valid target for counterspell.

This leads us to your "small arcane focus". If the component can be hidden from view then while in a state of being hidden from the counterspell caster they may or may not see it or the spell. The onus is on them to do so, the mere fact that an arcane focus of some sort is involved does not make them see it, it merely makes it possible.

It should require a perception roll by the counterspell caster whenever no components are being used in an obvious manner, and is only possible where visual perception is possible (eg: no greater invisibility). Counterspelling when the focus is small and easily concealed should require a perception roll, perhaps contesting a slight of hand check.

If any spell with material components was automatically perceptible and automatically visually perceptible, then one could counterspell through walls, while blind, or against invisible opponents. Components are a necessary condition, not a sufficient one.

If it was not possible to discreetly cast a spell with material components under the table, from time to time, then the question arises: Can I do anything with minor illusion whatsoever?

\$\begingroup\$Why are you are not considering the relevant second part of the quote from BlueMoon's answer which seems to contradict your answer explicitly? "To be perceptible, the casting of a spell must involve a verbal, somatic, or material component. The form of a material component doesn’t matter for the purposes of perception, whether it’s an object specified in the spell’s description, a component pouch, or a spellcasting focus." If a spell has a component, it is perceptible according to the rules. No check needed.\$\endgroup\$
– RubiksmooseApr 20 at 21:32

\$\begingroup\$@Rubiksmoose Under my reading this is within the context of the material component being a necessary rather than a sufficient condition. It merely states that the same rule of necessity applies for all forms, not that it makes it sufficient, as in automatically seen. Beyond this it is unclear whether what you quote references the specific physical object''s form or simply (as the comma after perception would seem to imply) there being no difference based on which of these three arch-types of material component is being used.\$\endgroup\$
– Benjamin OlsonApr 20 at 21:58

\$\begingroup\$@Rubiksmoose And whatever the reading of the second sentence, your conclusion that it is automatically perceptible in no way logically flows from any content in the passage. It is clearly about necessary conditions not sufficient ones.\$\endgroup\$
– Benjamin OlsonApr 20 at 22:01